Hello IMMA,
Thank you for contacting National Instruments.
RS-232 is a single-ended data communication method, meaning it uses a single wire for transmission (two wires total - one wire is used to transmit and one to receive). You will need to use a serial cable, such as a null-modem cable, to pass data between your instrument and PC. RS-232 is also an asynchronous form of communication, which means it uses software and hardware buffers in lieu of a synchronizing clock. It will allow you to send commands to your instrument while receiving data at the same time.
To communicate with your HP34970 in LabVIEW using RS-232, you will need to use the Serial functions located on the Functions >> Instrument I/O >> Serial palette. There are a few useful exa
mples included with LabVIEW that demonstrate how to use these functions. You can locate these examples by going to Help >> Find Examples and searching with keyword "Serial." In most cases, you will configure your serial port, write a command to your instrument, receive data back from your instrument, and close your serial session.
I hope this helps! If you have any further questions, have trouble finding the examples, or need more help with serial communication, let me know!
Matthew C
Applications Engineer
National Instruments